Uninterrupted pump operation

1st August 2017

A progressing cavity pump in a remote oilfield provides a constant delivery rate regardless of the product viscosity

The transfer of crude oil always presents new challenges. In one recent example from the Tatarstan region of Russia, an oilfield required pumps that would reliably guarantee a constant delivery despite the very viscous crude oil with a high sand content, and widely fluctuating outdoor temperatures.

Crude oil with a high sand content is one of the most difficult conveying media: on the one hand, the consistency is not clearly predictable because of the constantly changing composition; and, on the other hand, the sand particles contained in the oil are highly abrasive.

The associated wear means that traditional pumps have to be repaired or even replaced frequently, which means either money for new systems or losses as a result of downtime.

The latter was simply not an option for the important main pumps on the system for a 24-hour operation and a pumping system that is set up outdoors, where temperature can sometimes drop to -40°C.

The progressing cavity pump experts at Netzsch therefore recommended the use of a total of eight of its proven Nemo progressing cavity pumps, which were specially adapted for these adverse conditions and guarantee absolute reliability for at least 10,000 hours, which means over one year in continuous operation.

A drop in the delivery rate can be offset by an increase in speed on the pump unit. This allows the timely planning of services and the avoidance of downtimes.

In the specific case in Tatarstan four Nemo Type NM125SY progressing cavity pumps were chosen, each with a differential pressure of 18 bar, a pumping capacity of 120-220m3/h and drive power of 250kW as well as four Type NM148SY pumps, each with a differential pressure of 30 bar, a pumping capacity of 70-155m3/h and drive power of 250kW too. These are installed in an oilfield where the conveyed crude oil contains up to 3% sand.

The pumping system was designed in such a way that the mixture of oil and sand is transferred to a central treatment station. This permits an effective reduction in the operating costs.

Two 70km long pipelines are fed from the eight pumps in total. As the sand content is so high, the mixture must be pumped to a separator system for further processing where the solids and some of the water in it are separated.

The Nemo pump displays one of its main advantages here: it considerably facilitates the separation process with the smooth, low-pulsation conveyance of product because it does not mix the phases in the conveying process and therefore significantly assists the separation.

A further challenge that the pumps in Tatarstan have to meet is the viscosity of the crude oil as well as its fluctuating pressure between summer and winter due to the high outdoor temperature differences, which is why the pumps used require an additional control range.

Initially the plan was to install Notos multi-screw pumps from Netzsch to replace the existing pumps from a different manufacturer. However, after detailed examination of the application, the customer was advised to use the Nemo pumps.

Problems can be expected with multi-screw pumps even with special coatings due to the high sand content.

Netzsch therefore recommended the Nemo pumps as they are distinguished by their easily controllable, low shear pumping system with solid matter compatibility at the same time.

The local requirements as well as the service structures of the component suppliers were taken into account during the consultation.

A special low-temperature version of the progressing cavity pumps is used for the project in Tartastan including a drive with a gearbox, couplings and bearings.

The customer has confidence in the expertise and good experience that Netzsch has gained in the operation of previously installed Nemo pumps of a similar size.

These pumps run in uninterrupted operation without maintenance and to the complete satisfaction of the customer.